Sonic Boom 4
Apart from the supersonic Concorde, the fastest commercial way to fly is in a Boeing 747 at around 885 kph - about 85% of the speed of sound. Supersonic flight would get you there very much faster. But everybody thinks that destructive sonic booms are an essential part of supersonic travel. However, there are many factors that influence the loudness of the sonic boom down on the ground. They include the weight, shape and size of the aircraft, as well the plane's altitude, attitude (nose-up or nose-down), flight path and the local weather conditions. Fooling around with some of these could make a supersonic plane acceptably quiet.
For example, back in the 1970s, Richard Seebass from the University of Colorado in Boulder, worked out that you could virtually eliminate the sonic boom by making the nose of the plane blunt. This blunt nose would heat up the air in front of the plane, and would also stretch the bow shock wave out a long way in front of the plane. So there wouldn't be a sudden jump in pressure, that would give the offensive shock wave down on the ground. But H. K Cheng, a retired Aeronautical Engineer formerly with the Department of Aerospace Engineering at the University of Southern California, has a modern Star Wars version of this - it uses a laser to heat up the air in front of the plane.
In 2001, the United States Defence Advanced Research Projects Agency allotted some $70 million to three manufacturers to work out how to make supersonic planes more quiet. The companies (Boeing, Lockheed Martin and Northrop Grumman) are each trying different approaches.
John Morgenstern, an Aeronautical Engineer and expert in sonic booms from the Lockheed Martin Skunk Works in California, has come up with a very neat way of effectively blunting the nose of a plane. His design has a little flap that pushes forward from the nose of the aeroplane. Not only does it stretch out the shock wave coming from the nose, it also creates an extra bit of lift, which cuts the fuel consumption. In 1999, he published a patent with an even more daring design, which has a longer nose and a V-shaped tail.
Domenic Maglieri from Eagle Aerospace in Hampton Virginia has an even wilder design - a supersonic biplane. This would spread the lift over more surface area of wing, and so reduce the sonic boom. Heinz Gerhardt, an aeronautical engineer from Northrop Grumman in Los Angeles likes this idea so much that he has designed a family of supersonic biplanes.
At this stage, all the big companies are keeping quiet. But Gulfstream (which is funding its own research) reckons its supersonic business jet will be flying in around six years time, while the Russian Sukhoi Company reckons their supersonic bizjet will fly in 2010.
And of course, in the backs of their minds, the companies are all thinking of big supersonic jets that can carry a big number of people a big distance, and so generate big bucks. You see, for all of its speed, the Concorde has only a short range, which is fine for flying across the Atlantic, but hopeless for flying across the Pacific or around the Pacific Rim.
The new supersonic designs aim for a maximum overpressure of just 0.3 pounds per square foot.
But as well as new shapes, the new supersonic planes will need radically new engines. The Concorde engine is fine at Mach 2.2, but it's very thirsty and noisy on take-off and landing.
Rolls Royce, on the other hand, has decided to modify the existing giant engine that powers the Boeing 777 with 95,000 pounds of thrust. This enormous engine is bigger in diameter than the body of a Boeing 737. Rolls Royce want to remove the huge fan off the front, and in this form, it should just meet take-off and landing noise requirements.
These supersonic bizjets will still burn up a lot of fuel. But if you can afford a$160 million plane, the cost of a few extra tonnes of fuel will be no worry at all.
So once the supersonic flight industry loses the boom, business should start to bloom.
Published 18 April 2002
© 2024 Karl S. Kruszelnicki Pty Ltd
